You definately need a good second opinion on this matter.
Low platelets, can be found in quite a few illness,s and those need ruling out.
Thrombocytopenia, ITP, APS, and also bone marrow conditions. etc etc.
I had a low blood platelet count, but it was linked to my auto-immune disease of APS.
This needs attention . If they arent clever enough to give you a reason why, then you need someone else.
Dont give up searching.